Narrative of the surveying voyages of his majesty's ships Adventure and Beagle (vol.2- Appendix): between the years 1826 and 1836 : describing their examination of the southern shores of South America, and the Beagles's circumnavigation of the globe

290 APPENDIX. from each side, that the western portion of this zone is affected. Otaheite is thus at the edge, or Umit, of four tides — one east, ano- ther west, a third to the north, and a fourth to the south, and as these tides are moving with different impulses, and at different times, it is not at all surprising that they should almost neutralize each other at Otaheite. As we go west or east of that island, we find the tides augmenting gradually in height. At the Friendly Islands they rise five feet, and at the Gambier Islands three feet. Respecting the twelve hour tide at New Ireland, and at other places in the Indian archipelago — appeal to facts, so far as we can trace the tides at present, tends to confirm the explanation of Sir Isaac Newton, which consisted in supposing that such tides are com- pounded of two tides, which arrive by different paths, one six hours later than the other. " When the moon is in the equator, the morning and evening tides of each component tide arc equal, and the tides obhterate each other by interference, which takes place about the equinoxes. At other periods the higher tides of each com- ponent daily pair, are compounded into a tide which takes place at the intermediate time, that is, once a day ; and this time will be after noon or before, according to the time of year." — Whewell, in Phil. Trans. 1833, p. 224. At New Ireland, the time of high water is about 3 ; but at New Caledonia it is 9. Again, at the north-west coast of Australia, it is 12 ; and at the eastern approach to Torres Strait, 10 : at the Philip- pine Islands it is 4 ; and at Loo Choo, 10. Now here are various times of tide, and different impulses, crowded together into a com- paratively small space, sufficient to perplex any theorist of the pre- sent day. Owing to local configurations, and a variety of inci- dental circumstances, we find every kind of tide in this region, in a space sixty degrees square. Although tidal impulses, waves, and resulting currents are checked and altered by the broken land of the Indian archipelago, they cannot be suddenly destroyed, or prevented from influencing each other, while communications, more or less open, exist in so many directions. At the Sandwich Islands there is said to be very little tide. As it is high water in 40° N., on the American coast, at 8 ; at which time it is also high water at the Galapagos, it appears that the two zones of the ocean — one about the equator, and the other near 40° N. — have liigh water, in the mericUan of the Sandwich Islands, at two